The state of the art with regard to radio reception and receivers, particularly with regrad to receivers for personnel location, is described inter alia in Patent Application GB No. 2101779A, published in January 1983. Therein is discussed a personnel locator adapted for receiving calls sent by radio and for receiving and storing a plurality of messages and for displaying one message at a time in a display window. The received message is compared with each of the already stored messages and is stored in the memory of the receiver only if it differs from all of the messages already stored. With the intention that the probability should be increased that the message is properly received, it is sent repeatedly, but the mentioned comparison prevents it being stored more than once.
A weakness in the thus described personnel locator is that if a character in one of the received messages has been received in a distorted state, the comparison cannot shown that the same message has been received, and different versions of the same message will be stored twice and possibly several times.
In addition to the above-mentioned application, an example of the method of sending and receiving personnel locator calls is described in: "Final Report of the British Post Office Code Standardisation Advisory Group (POCSAG)", London 1978.